Modern vacuum cleaners are typically either “bagged” or “bagless”.
Bagged machines can suffer loss of suction during use, which is caused by a progressive blocking of the pores of the filter bag with dust.
Bagless machines typically rely on cyclonic dust separation rather than a filter bag. These machines maintain much better suction than bagged machines, because cyclonic separators do not tend to block as easily as filter bags. But cyclonic separators are relatively complex in layout compared to a filter bag—which can make them difficult to package effectively in the machine. This difficulty increases with dual-stage cyclonic separators, which may require relatively complicated ducting paths to connect the two separate cyclonic stages making up the separator, particularly if one of those stages is multi-cyclonic.